The present invention relates to a multiport cylinder dryer having improved thermal resistance and improved heat transfer for use in drying pulp and paper.
The pulp and paper industry is among the most capital intensive manufacturing industries in the United States. The large dryers that remove residual water from the pulp and paper are the costliest components associated with papermaking. These dryers also consume more energy than other components of the paper machine and offer significant opportunities for applying cost saving measures. A need exists for a mechanism to significantly improve the heat transfer from conventional steam cans.
Conventional steam dryer cans are simply large cast iron cylinders into which pressurized steam is used to heat the cylinder walls. This type of steam can is a very simple heat transfer device. Heat is transferred from the steam inside the dryers to the wet sheet outside the dryers, providing the energy required for evaporation. As the heat is transferred from the steam, most of the steam condenses inside the dryer cans. The condensation that is formed often interferes with heat transfer to the wall.
Drying is one of the most common unit operations used in diverse processes in the agricultural, ceramic, chemical, food, pharmaceutical, pulp and paper, mineral, polymer, and textile industries. Therefore, the dryer technology is crosscutting with a range of applications and many industries could expect significant benefits from an improved cylinder dryer.
A principal object of the present invention is an improved cylinder dryer for use in drying pulp and paper and the like.
It is another object of the present invention to provide such an improved cylinder dryer having improved thermal resistance and improved heat transfer.
It is another object of the present invention to provide a multiport cylinder dryer having improved thermal resistance and improved heat transfer for use in drying pulp and paper and the like.
It is another object of the present invention to provide such multiport cylinder dryer for maximizing drying rates in drying pulp and paper and the like.
It is another object of the present invention to provide such multiport cylinder dryer for maximizing drying rates in drying pulp and paper and the like by maximizing heat transfer from steam into the material to be dried, such as pulp and paper and the like.
In brief, a multiport cylinder dryer for use with drying a web of pulp, paper, or similar material, and a method for drying a moving web of pulp, paper, or similar material are provided. The multiport cylinder dryer includes an outer cylinder dryer surface for transferring heat to a moving web to be dried. A plurality of multiport flow passages are positioned close to the outer cylinder dryer surface. The multiport flow passages are arranged for channeling steam flow for heating the cylinder dryer surface.
In accordance with features of the invention, the multiport cylinder dryer achieves significantly higher drying rates than conventional dryers by minimizing the condensate layer and maximizing the heat transfer surface area. The dominant heat transfer mode in the multiport cylinder dryer is convection, which is significantly more effective than conduction, the dominant heat transfer mode in conventional dryers.